LifetimeDependence inference, dont use BitwiseCopyable type as candidate

Author: meg-gupta

lib/AST/LifetimeDependence.cpp

@@ -172,6 +172,18 @@ static LifetimeDependenceKind getLifetimeDependenceKindFromDecl(
                                   : LifetimeDependenceKind::Inherit;
 }
 
+static bool isBitwiseCopyable(Type type, ModuleDecl *mod, ASTContext &ctx) {
+  if (!ctx.LangOpts.hasFeature(Feature::BitwiseCopyable)) {
+    return false;
+  }
+  auto *bitwiseCopyableProtocol =
+      ctx.getProtocol(KnownProtocolKind::BitwiseCopyable);
+  if (!bitwiseCopyableProtocol) {
+    return false;
+  }
+  return (bool)(mod->checkConformance(type, bitwiseCopyableProtocol));
+}
+
 std::optional<LifetimeDependenceInfo>
 LifetimeDependenceInfo::fromTypeRepr(AbstractFunctionDecl *afd) {
   auto *dc = afd->getDeclContext();
@@ -205,14 +217,9 @@ LifetimeDependenceInfo::fromTypeRepr(AbstractFunctionDecl *afd) {
     // error.
     // TODO: Diagnose ~Escapable types are always non-trivial in SIL.
     if (paramType->isEscapable()) {
-      if (ctx.LangOpts.hasFeature(Feature::BitwiseCopyable)) {
-        auto *bitwiseCopyableProtocol =
-            ctx.getProtocol(KnownProtocolKind::BitwiseCopyable);
-        if (bitwiseCopyableProtocol &&
-            mod->checkConformance(paramType, bitwiseCopyableProtocol)) {
-          diags.diagnose(loc, diag::lifetime_dependence_on_bitwise_copyable);
-          return true;
-        }
+      if (isBitwiseCopyable(paramType, mod, ctx)) {
+        diags.diagnose(loc, diag::lifetime_dependence_on_bitwise_copyable);
+        return true;
       }
     }
 
@@ -426,16 +433,11 @@ LifetimeDependenceInfo::infer(AbstractFunctionDecl *afd) {
   if (!cd && afd->hasImplicitSelfDecl()) {
     Type selfTypeInContext = dc->getSelfTypeInContext();
     if (selfTypeInContext->isEscapable()) {
-      if (ctx.LangOpts.hasFeature(Feature::BitwiseCopyable)) {
-        auto *bitwiseCopyableProtocol =
-            ctx.getProtocol(KnownProtocolKind::BitwiseCopyable);
-        if (bitwiseCopyableProtocol &&
-            mod->checkConformance(selfTypeInContext, bitwiseCopyableProtocol)) {
+      if (isBitwiseCopyable(selfTypeInContext, mod, ctx)) {
           diags.diagnose(
               returnLoc,
               diag::lifetime_dependence_method_escapable_bitwisecopyable_self);
           return std::nullopt;
-        }
       }
     }
     auto kind = getLifetimeDependenceKindFromType(selfTypeInContext);
@@ -463,9 +465,13 @@ LifetimeDependenceInfo::infer(AbstractFunctionDecl *afd) {
       continue;
     }
     auto paramOwnership = param->getValueOwnership();
-    if (paramTypeInContext->isEscapable() &&
-        paramOwnership == ValueOwnership::Default) {
-      continue;
+    if (paramTypeInContext->isEscapable()) {
+      if (isBitwiseCopyable(paramTypeInContext, mod, ctx)) {
+        continue;
+      }
+      if (paramOwnership == ValueOwnership::Default) {
+        continue;
+      }
     }
 
     auto lifetimeKind = getLifetimeDependenceKindFromType(paramTypeInContext);

test/Sema/implicit_lifetime_dependence.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature NonescapableTypes -enable-experimental-feature NoncopyableGenerics
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature NonescapableTypes -enable-experimental-feature NoncopyableGenerics -enable-experimental-feature BitwiseCopyable
 // REQUIRES: asserts
 
 struct BufferView : ~Escapable, ~Copyable {
@@ -24,7 +24,15 @@ struct ImplicitInit3 : ~Escapable, ~Copyable { // expected-error{{cannot infer l
   let mbv2: BufferView
 }
 
-func foo() -> BufferView { // expected-error{{cannot infer lifetime dependence , no parameters found that are either ~Escapable or Escapable with a borrowing ownership}}
+func foo1() -> BufferView { // expected-error{{cannot infer lifetime dependence, no parameters found that are either ~Escapable or Escapable with a borrowing ownership}}
+  return BufferView(nil, 0)
+}
+
+func foo2(_ i: borrowing Int) -> BufferView { // expected-error{{cannot infer lifetime dependence, no parameters found that are either ~Escapable or Escapable with a borrowing ownership}}
+  return BufferView(nil, 0)
+}
+
+func foo3<T: _BitwiseCopyable>(arg: borrowing T) -> BufferView { // expected-error{{cannot infer lifetime dependence, no parameters found that are either ~Escapable or Escapable with a borrowing ownership}}
   return BufferView(nil, 0)
 }